Most low-caloric sweeteners are synthetic organic compounds like saccharine and cyclamate or more recently, biochemicals such as aspartame, a dipeptide. Their taste characteristics are not easily altered or modified. Due to the quantity of material required to elicit a sweet taste sensation, the amount consumed is high enough to warrant caution concerning their use. In addition, the possibility of their conversion during the processing of the food product to other less safe compounds has also slowed their general acceptance. Thaumatins are a class of natural proteins with a sweet taste many thousand fold more intense than sugar. The gene has been cloned and an expression system developed at INGENE. By random mutation, over one hundred altered proteins have been expressed and taste tested. Many characteristics have been identified and scored, such as persistence, after-taste and stability. The structure of the native protein and each of the mutant forms will be determined at Cryschem in order to elucidate the structure-function relations. Mapping the thaumatin domains that influence the perception of sweetness also provides insight into the structure of the sweet taste receptor. Based on these structures, second generation protein sweeteners with specific desirable characteristics can be designed.